Interesting project for low cost NAS. However, why is it open to air? It seems to me that it would gather quite a bit of dust and be susceptible to damage. Is this required for fanless operation?
As far as fanless micro computers go, they usually tend to go with an enclosed design with the unit itself acting as a giant heat sink. However, with this many disks, maybe it needs an open design? Possibly only for cost.
They say that fan cooled enclosures collect more dust. I can confirm. I have a ReadyNAS NV+ with a 92mm fan and it accumulates tons of dust extremely quickly.